Conventionally, there is a communication scheme using OFDM broadly known as the radio base-station apparatus. Meanwhile, adaptive array antenna technology is now under study aiming at increasing the traffic capacity, broadening the communications area, suppressing the interference and the like. Attentions are drawn to the applications of the adaptive array antenna technology of the OFDM scheme. For example, there are those, including a description in JP-A-11-205026. This publication describes that a transmission/reception weight is computed on the basis of an interval of OFDM sub-carrier frequencies and an interval of array-antenna elements, so that weighting is carried out based on each sub-carrier thereby implementing directional transmission/reception.
In this conventional art, by setting transmission and reception weights for each sub-carrier, it is possible to eliminate the deviation of directional beam pattern that occurs at the interval of sub-carrier frequencies. However, where amplitude or phase deviation takes place at between transmitting/receiving branches, the formed beam pattern would deviate from the desired beam pattern. The radio-frequency circuit section, as a constituent element of each transmitting/receiving branch, is configured with many analog elements. These analog elements cause a characteristic deviation because of the difference between individual elements. Furthermore, the characteristic is varied by surrounding temperature, lapsing time and so on. By such analog element characteristic, amplitude/phase deviation is caused between the transmitting/receiving branches. Particularly, it is considered that, on a broadband signal such as an OFDM signal, a frequency characteristic is caused in the amplitude/phase deviation between the branches. Meanwhile, on the lines up to the antenna element, there occurs a difference in delay time between the transmitting branches because of the difference of line length to the antennas or line characteristic. From these factors, the amplitude/phase relationship set in transmission weight readily collapses between the antenna elements, making it impossible to obtain an ideal beam pattern. Meanwhile, there is a drawback that, in the case a broadband signal is sent, a different pattern of beam is possibly formed based on the frequency resulting from a deviated frequency characteristic.